Upholding and enforcing the longstanding global norm against chemical weapons – while deterring Bashar al-Assad from using them again against his own people – offers a compelling rationale for even a punitive use of force by the United States against Syria. Tuesday night, Barack Obama made a semblance of that argument; but he lathered it in so much threat-exaggeration and maudlin imagery that it was virtually impossible to take his case for war seriously.

If anything, the fact that Obama was forced to rely on contradictory and deceptive arguments to sell the American people on the idea of military intervention in Syria did more to undermine the case for intervention than reinforce it.

The best argument for the use of US military force against Syria is actually a rather simple one: international norms dictating how wars are fought and how civilians are treated in wartime matter because they make wars less likely to occur. And when wars do happen, those norms ensure that that conflicts are just a bit less deadly.

In fact, the reason we uphold and enforce norms, like those on chemical weapons, is not because the world is a hotbed of violence, but actually, because it's never been safer. Sometimes, it is necessary to punish behavior that goes far beyond commonly accepted international norms and legal rules governing armed conflict.

Of course, such universalist, almost symbolic arguments are not easy ones on which to base a military intervention. And so it is perhaps not surprising that Obama felt the need to broaden his message … into the world of the fantastical.

Obama claimed, for example, that US "troops would again face the prospect of chemical warfare on the battlefield," if nothing was done about Assad's actions. He said, "it could be easier for terrorist organizations to obtain these weapons and to use them to attack civilians"; and he claimed "al-Qaida will only draw strength in a more chaotic Syria if people there see the world doing nothing to prevent innocent civilians from being gassed to death."

But none of these arguments makes much logical sense. Countries don't use chemical weapons against the US because: a) most don't have them; b) they are rather ineffective as a war-fighting tool; and c) countries rightfully fear the repercussions of using banned weapon against the United States for reasons that should be obvious to a president who said the American military doesn't do "pinpricks". Responding or not responding to Syria's use of chemical weapons likely won't change that calculus.

In addition, the desire of nihilistic terrorist organizations to obtain weapons of mass destruction will be little affected by the world's reaction to Assad's behavior. Groups like al-Qaida sought such deadly tools before the Syrian civil war, and they will seek them after. Indeed, the reference to al-Qaida in Obama's speech was nothing but a domestic dog-whistle, intended to scare Americans about the price of inaction. It glosses over the fact that an attack against the Syrian regime would inevitably hinder its war-making abilities – and make it more likely that radical jihadist groups would gain the upper hand in the Syrian civil war.

Obama's speech was filled with just these sorts of contradictions. On the one hand, he argued that "if fighting spills beyond Syria's borders, these weapons could threaten allies like Turkey, Jordan and Israel", but then said later that "neither Assad nor his allies have any interest in escalation that would lead to his demise. And our ally, Israel, can defend itself with overwhelming force." Well, which is it?

He said that "as the ban against these weapons erodes, other tyrants will have no reason to think twice about acquiring poison gas and using them." But he also pointed out that 189 countries have signed up to the Chemical Weapons Convention, which suggests that the broad consensus against the future use of chemical weapons is perhaps stronger than Obama is suggesting.

This was somewhat par for the course in a speech where Obama, in one breath, declared America is an "exceptional" nation and, in the next, promised the US would act with humility. What was perhaps most troubling about Obama's presentation is the questions that were left unanswered.

What if Assad goes back to gassing his people with chemical weapons? Will the US further escalate? Why are the horrors of children killed by chemical weapons qualitatively different from the horrors of children killed by artillery or machine guns?

Finally, what is the justification for condemning one violation of international law (the use of chemical weapons) with the violation of another (fighting a war in Syria without a UN security council mandate)? Does this set a troubling precedent for conflicts down the road?

To be sure, there are reasonable answers to these questions, but in failing even to try to answer them, and instead, raising red-herring issues and making dubious claims – such as, attacking Syria will "make our own children safer over the long run" – Obama offered the American people a confusing and ultimately misleading rationale for military action.

President Obama is hardly the first president to take such liberties when making a justification for US intervention. But for a candidate who ran for president on his principled opposition to the Iraq war, more should be expected than simply the same old, same old.

There is a complex and challenging case to be made for military intervention in Syria. Instead of venturing down that more difficult path, President Obama, last night, took the easier, expedient and disingenuous route to finish the deal. The American people deserved better.